1. Field of the Invention
This invention relates to a linear synchronous motor powered vehicle.
2. Description of the Prior Art
In the case of driving a vehicle, generally, adhesion is utilized which exists between the rail or the road and the wheels supporting the vehicle body to which the rotational power caused by the driving motor carried on the vehicle body is transferred through the reduction gear system. This vehicle running by adhesion, however, is inappropriate for a high speed running, for example, of more than 300 km/h. This is because, when the running speed thereof increases to be in excess of 300 km/h, the adhesion between the wheel and the road (or the rail) decreases abruptly.
This brings about efforts of searching for something other than the adhesion as a factor to drive the vehicle. Some of them have succeeded heretofore in practical use. One successful way is where the vehicle is driven without transmitting the driving force to the wheel. An example of such an idea, i.e. non-adhesion driving apparatus, is a linear motor where an electric motor operating in rotational mode is modified to a linear structure operating in linear mode.
In this linear motor category, there is a motor system wherein a group of magnetic devices of the linear motor is mounted on the vehicle body while another group of magnetic devices thereof are mounted on the road along the track thereon, and the same principle as that of the synchronous motor causes the vehicle to drive.
The present invention pertains to a vehicle powered by, particularly, the linear synchronous motor just mentioned in the linear motor category. An example of the linear synchronous motor powered vehicle of prior art will be described hereinafter with reference to FIGS. 1 and 2. In the figures, a vehicle body 1 supported by the wheels 2 moves along the rail constructed on the ground E, the vehicle body being provided at the bottom with superconductive field coils 4 substantially parallel with the ground E. A series of the field coils 4 are disposed on the vehicle body 1 in the longitudinal direction thereof, while the adjacent field poles are opposite in polarity to each other. Armature coils 3 being connected through a switching means to a power supply, are mounted along the rails on the ground facing up to the field coils 4. The armature coils 3 energized by the power supply, develop a shifting flux wave while the field coils 4 develop a magnetic field. The travelling magnetic flux wave interacts with the magnetic field thereby producing a driving force to drive or propel the vehicle body 1.
The linear synchronous motor powered vehicle just described is of a type that the vehicle body 1 is supported by the wheel 2. The linear synchronous motor may also be applicable to such a type of vehicle where the vehicle body 1 is supported by using the levitation magnetically caused, as shown in FIG. 3.
In FIG. 3 illustrating the magnetically levitated vehicle, two pairs of superconductive coils 6A and 6B, and, 7A and 7B, are mounted in a housing 5 at the bottom of the vehicle body 1. The respective super-conductive coils 6A and 6B are mounted, facing the ground E, on the bottom of the two U-shaped portions of the housing 5. The field coils 7A and 7B are mounted, facing each other, at the reversed U-shaped portion of the housing at the center thereof. The field coils 7A and 7B are disposed normal to the field coils 6A and 6B. The ground E is provided with the levitation coils 10A and 10B and the field coils 6A and 6B, the former confronting the latter. A stabilizing coil 8 is disposed between the field coils 7A and 7B. The levitation coils 10A and 10B and the stabilizing coil 8 are all short-circuited or each of them are constructed of a conductive single sheet. The armature coil 9 for the linear synchronous motor is located between the levitation coils 10A and 10B. The propulsion of the vehicle body 1 in this case is made in the same manner as described above (FIGS. 1 and 2). That is to say, the vehicle body is driven by the driving force caused by the interaction of the travelling flux wave developed by the armature coil 9 with the magnetic field developed by the field coils 7A and 7B. As the vehicle body 1 moves, magnetic mutual repulsion occurs between the field coils 6A and 6B and the corresponding the levitation coils 10A and 10B, between the field coils 7A and the stabilizing coil 8, and between the field coil 7B and the stabilizing coil 8. By this mutual repulsion therebetween, the vehicle body is levitated with stabilization.
These field coils mentioned above, 4, 6A, 6B, 7A, and 7B, i.e. the field poles 12, are normally disposed on the vehicle along the length L thereof, as shown in FIG. 4. What are mounted on the vehicle, however, are not only these magnetic poles but also an auxiliary power supply, a cooling system, and other devices. Further, the place on the vehicle body where such systems or devices are to be mounted is confined to the underfloor thereof. Thus, it is not possible to use the entire underfloor of the vehicle 1 for mounting the magnetic poles 12. Thus, in actual practice, a compromise is made and the area for mounting the field poles 12, e.g. the length of the field pole 12, is reduced for securing the necessary equipment such as the auxiliary power supply, the cooling system, and other devices. Accordingly, it is necessary to make the length of the field pole 12 somewhat shorter than a pole pitch P. Here, the pole pitch P is defined as the interval between the adjacent field poles in the continuously disposed ones.
This sizable reduction in the length of the field pole 12 brings about various disadvantages. One of them is to produce a noticeable pulsation in the propulsion. In the case of linear synchronous motor, there are produced the right and left directional force and the up and down directional force, besides the propulsion. These forces exhibit large pulsations similar to that in the propulsion as shown in FIG. 5, resulting in discomfort to the passengers, as well as undesirable effects on the vehicle body, in particular, the vehicle of such a type that its body is magnetically levitated.
It is obvious that, when the length of the field pole is shorter than the pole pitch P, the pulsation occurs in the propulsion. That is to say, the flux distribution caused by the field poles are uneven all over the pole pitch P, with a low flux density at the both ends. In other words, the shorter the length that the field pole 12 is with respect to the pole pitch P, the narrower the uniformity region of the flux density becomes. For this reason, the propulsion decreases at certain positions of the vehicle.
The vehicle body 1 is provided at its both ends with couplers 11 for coupling with the adjacent vehicle bodies. Accordingly, the length L of one vehicle including the couplers is more elongated, and thus the pole pitch also is enlarged. On the other hand, with the actual field pole 12 is impossible to make an elongation of the length thereof, since it has the restriction above mentioned of the elongation thereof. Thus, the length of the field pole 12 is sizably shorter than that of the pole pitch P so that a larger pulsation occurs in the propulsion, the right and left directional force, and the up and down directional force.
There are some countermeasures to restrict such a detrimental pulsation. One of them is to use the field poles 12 whose length is substantially equal to the pole pitch P. This method, however, has a disadvantage in that the place for mounting the necessary equipment such as the auxiliary power supply, can not be secured. An easy way to secure the place for the necessary equipment is to enlarge the cross section of the vehicle body by the space required to accommodate the necessary equipment.
This method of simply enlarging the cross section thereof, however, is accompanied by various problems. That is, air resistance increases when the vehicle is running, and the weight of the vehicle body also increases. For this reason, a larger capacity power source is required to drive the vehicle of such a structure, and the manufacturing cost is high.
Accordingly, the only way to restrict the pulsation occuring in the propulsion, the right and left directional force, and the up and down directional force to obtain a comfortable ride for the passengers is to bring the field pole length close to the optimum length allowing it to be substantially equal to the pole pitch.